Clean burning wood fiber fuel pellets and its method of manufacture

ABSTRACT

Clean burning wood fuel pellets. The clean burning wood fuel pellet includes a mixture containing wood chips and calcium carbonate.

BACKGROUND OF THE INVENTION

The present invention generally relates to wood fiber fuel pellets. Moreparticularly, the present invention relates to clean burning wood fiberfuel pellets and its method of manufacture.

Due to diminishing quantities of coal, petroleum, and natural gasproducts, attention is being directed to found renewable fuel sources ofenergy. With the growing interest in renewable energy, the use of woodfuel pellets has increased considerably. Unfortunately, the smokeproduced by the burning of wood fuel pellets contains numerous chemicalsthat are harmful to the environment.

As can be seen, there is a need for a wood pellet fuel product that maybe burned without producing harmful smoke to the environment.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a clean burning wood fuel pelletincludes a mixture containing wood chips and calcium carbonate.

In another aspect of the present invention, a method for producing cleanburning wood fuel pellets, the method including the steps of: mixingcalcium carbonate and wood chips to form a mixture and forming pelletswith the mixture.

These and other features, aspects and advantages of the presentinvention will become better understood with reference to the followingdrawings, description and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a flow diagram for producing clean burning wood fuelpellets according to an exemplary embodiment of the present invention;and

FIG. 2 illustrates a block diagram of a system for producing cleanburning wood fuel pellets 10 according to the exemplary embodiment ofFIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

The following detailed description is of the best currently contemplatedmodes of carrying out exemplary embodiments of the invention. Thedescription is not to be taken in a limiting sense, but is made merelyfor the purpose of illustrating the general principles of the invention,since the scope of the invention is best defined by the appended claims.

Various inventive features are described below that can each be usedindependently of one another or in combination with other features.

Broadly, embodiments of the present invention generally provide woodfuel pellets containing calcium carbonate. In addition, the presentinvention provides a method of producing the wood fuel pellets.

FIG. 1 illustrates a flow diagram for producing clean burning wood fuelpellets 10 according to an exemplary embodiment of the presentinvention.

These clean burning wood fuel pellets 10 may be manufactured by usingany conventional methods of producing wood fuel pellets as long as CaCo₃may be added during the manufacturing process. To better understand thepresent invention, the present invention may be explained by using oneof the several conventional methods of producing wood pellets.

The tree (not shown) may be cut into logs 12 of desired size. The logs12 may be transported by a conveyor belt 14 to a debarker 18. Thedebarker 18 may remove the bark (not shown) from the log 12. Thedebarker 18 may be a ring debarker, a drum debarker, or a Rosserheaddebarker. Next, the log 12 may be transported by a conveyor belt 14 to alog chipper 20. The log 12 may be fragmented into chips inside the logchipper 20. The size of the chips may depend on the specification of thehammer mill for continuous material flow. The chips (not shown) may befed into a chip bin 22, which feeds a conveyor belt 14 powered by amotor 40 controlled by a variable speed drive 42. The conveyor belt 14transports the chips (not shown) to a screen fee bin 34 prior toentering a shaker screen 32. Inside the shaker screen 34, the chips maybe separate depending on their size. In some embodiments, thepredetermined size may be ¼ of an inch. Chips (not shown) having a sizegreater than the predetermined size, may be fed to a hopper 36 connectedto a screw conveyor 16. The screw conveyor 16 may be powered by a motor40 controlled by a variable speed drive 42. The screw conveyor 16 maytransport the chips (not shown) having a size greater than thepredetermined size to a hammer mill 30 to further reduces the size ofthe chips (not shown). The output of the hammer mill 36 may be fed intoa conveyor 14 operatively connected to a bin 28 containing the chips(not shown) having the predetermined size. Chips (not shown) having asize of less than the predetermined size, may be fed to a hopper 38connected to a screw conveyor 16. The screw conveyor 16 may be poweredby a motor 40 controlled by a variable speed drive 42. The screwconveyor 16 may transport the chips (not shown) having a size of lessthan the predetermined size to the bin 28 containing the chips (notshown) having the predetermined size.

The bark (not shown) may be fed to a bark bin 24 which may be connectedto a screw conveyor 16 powered by a motor 40 controlled by a variablespeed drive 42. The bark (not shown) and the chips (not shown) presenton the bin 28 may be fed into a tumble dryer 26. The tumble dryer 26 maydry the chips and bark to a moisture content between about 11 and 19%.The tumble dryer 26 may be operatively connected to a conveyor belt 14powered by a motor 40 controlled by a variable speed drive 42. Theconveyor belt 14 may feed the dried chips and bark (not shown) to afinished chips hopper 44 which may be connected to a screw conveyor 16powered by a motor 40 controlled by a variable speed drive 42. The screwconveyor 16 may transport the dried chips (not shown) into a mixingconveyor belt 63. A predetermined amount of CaCO₃ may be fed into themixing conveyor belt 63 by a dispenser 46. The mixing conveyor 63 mayfeed the mixture into a mixing bin 48. The mixing bin 48 may beoperatively connected to a screw conveyor 16 powered by a motor 40controlled by a variable speed drive 42. The mixture (not shown) may befed into a pellet mill 52. No binding agents may be added to the pelletmill 52. The mixture (not shown) may be then pelletized inside thepellet mill 52 forming the clean burning wood fuel pellets 10. The cleanburning wood fuel pellets 10 may have a length/diameter ratio of 2:1 tooptimize the combustion and emission process. The clean burning woodfuel pellets 10 may be transported by a cooling conveyer 50 into a cleanburning wood fuel pellets bin 54. Then, the clean burning wood fuelpellets 10 may be transported by a screw conveyor 16 to a storage bin55. The user (not shown) may feed the clean burning wood fuel pellets 10to a boiler or stove 56. The boiler or stove 56 may emit heat 60 to thesurrounding areas. Ash 58 coming out of the stove or boiler 56 may havea low pH and may be used as filler for fertilizers and concrete. Gasemission 62 produced by the stove or boiler 56 may contain water andCO₂.

The amount of CaCO₃ added to the dried chips may represent between about0.2 to 2.0% weight of the dried chips before combustion. After a longperiod of trial, it has been that the addition of CaCO₃ at a rate ofabout 0.2% to 2% to the dried chips before combustion may greatly reduceor eliminate many of the pollutants by chemically reacting with theirmolecular structure. The CaCO3 may react with chemicals having a pH ofless than 7 (acids), changing the chemicals into water and carbondioxide The CaCO₃ may have a particle size between 0.2 mesh and 35microns. These ranges of particle size may allow the CaCO₃ to better mixwith the dried chips. In addition, these range of particle size may helpto speed the chemical reaction between the CaCO₃ and the acids.

Both hardwoods and softwoods may primarily contain three components:cellulose at about 40% to 50% by weight, hemicelluloses at about 20% to30% by weight and lignin at about 20% to 30% by weight. Studiesperformed by the present inventor have shown that hardwoods andsoftwoods produce different levels of pollutants, ash and heat. Thisrequires the addition of different levels of CaCO₃ during themanufacturing process to achieve the desired reduction of pollutants inthe emissions and the ash.

For example, burning 1 kg of wood may produce approximately 1.8 to 2.4 gof acidic acid. The chemical make-up of the acidic acid is 2CH₃COOH.When acidic acid reacts with calcium carbonate, the reaction createswater (H₂), carbon dioxide (CO₂) and calcium acetate [(CH₃COO)₂]. Thisbasically eliminates the largest occurring acid in the smoke and ash.

FIG. 2 illustrates a block diagram of a system 100 for producing cleanburning wood fuel pellets 10 according to the exemplary embodiment ofFIG. 1.

It should be understood, of course, that the foregoing relates toexemplary embodiments of the invention and that modifications may bemade without departing from the spirit and scope of the invention as setforth in the following claims.

1. A clean burning wood fuel pellet comprising: a mixture containingwood chips and calcium carbonate.
 2. The clean burning wood fuel pelletaccording to claim 1, wherein the mixture includes between about 0.2 to2.0% weight of the calcium carbonate.
 3. The clean burning wood fuelpellet according to claim 1, wherein the calcium carbonate has aparticle size between 0.2 mesh and 35 microns.
 4. The clean burning woodfuel pellet according to claim 1, wherein the clean burning wood fuelpellet emits heat, water, and carbon dioxide during combustion.
 5. Theclean burning wood fuel pellet according to claim 1, wherein the cleanburning wood fuel pellet have a length/diameter ratio of 2:1.
 6. Amethod for producing clean burning wood fuel pellets, the methodcomprising the steps of: mixing calcium carbonate and wood chips to forma mixture; and forming pellets with the mixture.
 7. The method of claim6, further comprising the step of drying the wood chips prior to mixingwith calcium carbonate.
 8. The method of claim 6, wherein the mixtureincludes between about 0.2 to 2.0% weight of the calcium carbonate. 9.The method of claim 6, further comprising the step of cutting the woodchips to ¼ of an inch prior to mixing with the calcium carbonate. 10.The method according to claim 6, wherein the calcium carbonate has aparticle size between 0.2 mesh and 35 microns.